After years of disappointment, clinical-trial results released on 22 July suggest that antibody treatments may produce small improvements in people with Alzheimer’s disease.

The drugs — Eli Lilly’s solanezumab and Biogen’s aducanumab — target the amyloid-β protein that accumulates in the brains of people with Alzheimer’s. Many researchers question whether the findings will hold up, given that antibody drugs against amyloid have failed in every previous test against the disease. Details of the results were presented at the Alzheimer's Association International Conference in Washington DC.

Lilly, of Indianapolis, Indiana, says that in a trial with 440 participants, solanezumab seemed to slow the cognitive decline of people with mild Alzheimer’s by about 30%. The loss of mental acuity in these patients over 18 months was equivalent to the deterioration that participants with a similar level of Alzheimer's disease in a placebo group experienced in just 12 months.

Lilly snatched this small victory from the jaws of defeat. In 2012, the company reported no difference between patients who had taken solanezumab for 18 months and those who had received a placebo. But when the company reanalyzed that trial it found a slight improvement in participants whose symptoms were mild when the trial began. Lilly continued the test for six months and began giving solanezumab to the 440-member control group, whose disease was by then more advanced.

At the meeting, Lilly showed that giving the drug to the 'late start’ group slowed their cognitive decline to match the rate seen in the 440 people who had been treated for the entire study. This suggests that the drug targeted the root of Alzheimer’s disease, rather than just relieving its symptoms.

Biogen, of Washington DC, presented results that show a moderate dose of its drug aducanumab reduced amyloid in 23 people, but did not have statistically significant clinical benefits. In March, the company reported that 27 people who received high doses of aducanumab for one year showed significantly less cognitive decline than people who received a placebo, and had less amyloid build-up in their brains.